Art or process of producing liquid air.



J. F. PLAGE. ART OR PROCESS OF PRODUCING LIQUID AIR.

1 APPLICATION PILEDNOV. 27, 1907. 918,468 Patented Apr. 13, 1909. 2 snmsws-snnm 1.

ART OR PROCESS OF PRODUCING LIQUID AIR.

APPLIOATION FILED NOV. 2'1, 1907.

J. F. PLACE.

Patented Apr. 13, 1909.

2 SHEETS-SHEET 2.

UNITED STATES PATENT OFFICE.

JAMES F. PLACE, OF GLENRIDGE, NEW JERSEY, ASSIGNOR TO AMERICAN AIR LIQUEFYING 00., A CORPORATION OF NEW YORK.

ART OR PROCESS OF PRODUCING LIQUID AIR.

Specification of Letters Patent. Patented April 13, 1909.

Application filed November 27, 1907. Serial No. 404,040.

the familiar principle called the fJoule-- Thompson effect, whereby a cumulative refrigerative result is obtained by expanding air through a throttled nozzle from a con- T all whom it may concern: Be it known that I, JAMES F. PLACE, a l citizen of the United States, and a resident i of Glenridge, in the county of Essex and nitrogen, or fractional distillation of the ii uid air as produced.

1 utilize the latentheat of vaporization of low-pressure liquid air, as set forth in my application Serial No. 334,104, but I make use of .the low temperatures obtained by expanding air in an engine and cooling the compressed air supplied to or expanded therein by the cold expanded air exhausted therefrom, as a part of the process or cycle herein.

In order that those skilled in the'art may make use of my invention, I will describe my present process, as illustrated by the accompanying drawings, in which- Flgure 1 is a diagrammatic view, partly in vertical section showing how I prepare the air for liquefactioncompress the same, ab-

' my improved process for cooling the air to sorb by chemical action and freeze out the moisture, remove the. CO, gas therefrom,

and precool that portion which is expanded in a closed cycle. Fig. 2 is a view in vertical sect1on of my improved counter-current system, showmg the mechanism I employ in be liquefied, by the vapor or cold expanding gases evaporated from low-pressure liquid an, reinforced in rcfrigerative effect by the 1' cold exhaust air expanded against external resistance in an air-expansion engine; also showing my process of liquefying in a submerged condenser, air compressed to substantially its critical pressure, by utilizing the latent heat required by liquid air in evaporating at substantially atmospheric pressure.

In my process set forth in Serial No. 334,104 I use an initial charge of liquid air to start the. rocess of liquefying air; or if such an initia l charge is not to be had, I provide for producing an initial charge by what is known as a throttled nozzle, availing of.

taincd) is instantaneous,

stant relatively high to a constant relatively low pressure. My present invention is based on a different method. I neither use nor require an initial charge of lir uid air, from an outside source; neither do I make use of the throttled nozzle, nor utilize the so-called Joule-Thompson eflect. I produce my initial charge of low-pressure liquid air, and constantly replenish the same, as desired, in part, by making use of the cold expanded exhaust air from an air-ex ansion engine, wherein I expand compresse air against external resistance; and afterusing this cold exhaust air to cool and liquefy air compressed to or above its critical pressure, I utilize it further for cooling the compressed air of less compression supplied to the engine for ex .ansion therein.

Wit my present process I also utilize the latent heat of vaporization required by liquid air at substantially atmospheric pressure, to

cool and liquefy air while at or above its critical pressure when there is no latent heat of condensation given out to neutralize refrigeration and retard liquefaction. It is well known that the critical pressure of air is about 39 atmospheres, and its critical temperature is '-220 F. It will condense to a liquid at 220 E, if it be compressed to about 39 atmospheres; and it will liquefy at a lower compression if cooled to a lower temperature, or at 'atmos heric pressure 1f cooled to 3]2.-6 F.; ut no amount of compression will cause liquefaction unless it be cooled to its critical temperature, namely, -220 F. If compressed to about 39 atmospheres and cooled to 220 F its density then as a gas is identical with its density as a liquid; and with the slightest lowering of the temperature then, its change of state from a gas to a liquid (if the pressure is mainand there can be no latent heat of condensation, as there is practically no further contraction.

By my present process I compress the air which is to be liquefied to about atmospheres (about 720 lbsgage), and liquefy all llo force or augment the refrigeration thereafter 'atinospheres (or about 176 lbs. gage).

All of the high-pressure air is liquefied in a condenser, having no outlet for air until after it is liquefied, and which is submerged in a constantly maintained charge of liquid air at substantially atmospheric pressure. This highly compressed air in-the submerged condenser being constantly maintained at or above its critical pressure, it consequently liquefies at 220 F.; while the temperature of the low-pressure evaporating'liquid air surrounding the condenser is constantly maintained at 312.6, or about 93 degrees colder. l/Vith these conditions, naturally the highly-compressed air in the sulnnerged condenser liquefies very rapidly, and is thereafter sub-cooled to about the temperature of the low pressure evaporating liquid air (-312.6); it is then released from pressure and is delivered to the low-pressure liquid air around the condenser to replenish the same, and in part is used to liquel'y a new supply of cooled high pressure air which has ta en its place in the condenser. That portion of the low-pressure liquid air which is evaporated during the process is conducted back over the incoming supply of compressed air, (first over that which is to be liquefied, and then over that which is to be expanded in the engine), in form of cold vapor and expanding air. The latent heat of condensation, given out by the high-pressure air in liquefying is, as stated herein, practically ml. The latent heat of vaporization required by the low-pressure evaporating liquid air is about 120 B t u. per pound, and this, with the cooling effect of the vapor and expanding air of the evaporated liquid (starting at 312 and absorbing heat. until it leaves the system at normal temperature), and the cooling effect of the cold expanded air from the engine (eqpivalent to the Work thereof)is all util- 1ze I. will now describe the appliances shown in the drawings to illustrate my improved process, in which similar reference characters refer to similar parts throughout.

In Fig. l the numeral 1 refers to the compressor for compressing the air expanded in the engine, shown only in outline at A in Fig. 2. This engine is of the ordinary reciprocat' ing type, with a cut-ofi valve, but is inclosed terial.

in an outer case packed with insulating ma- At 2 (see Fig. 1) I show an ordinary water cooler for removing the heat of compression; the compressed air from the compressor is passed t irough the water cooler to the discharge pi e 3, and is thence delivered with charges of lump calcium chlorid (5) in baskets or on shelves, 6. The air is assed 11111) through the drum in contact wit said 0 arges, and into pipe 7, from which it is deamass livering to the drip holder 15 and to the outlet pipe 16. g It is so constructed that there is an expanded air return-flow. passage 17 which will be referred to later on. The air now passes from pipe 16 to the thermal interchanger 51 (see Fig. 2). This consists of the triple helical descending coils 18 (to which the pipe 16 delivers) and which delivers to the engine feed pipe 19. From here the compressed air (at about 176 lbs. gage) is taken and expanded to atmospheric pressure against external. resistance on the piston rod 20.- The cold expanded air exhausted from the engine is conducted through the exhaust conduit 21 to the high-pressure airliquefier supply pipes 53, and passes up and over the same 111 the helical expanded air assage 22, and through passage 22 down et-ween the high-pressure triple coils23 into the passage 24. From here it passes up through the helical passage .25, formed between the engine supply triple coils 18, into the return-flow expanded air pipe 26, and through the pre-cooler helical passage 17 into pipe 26? and is thence delivered to the com- )ressor 1 (see Fig. 1) to be re-compressed for this air is used over and over in a closed circuit; and after ithas once been through the engine, then by closing valves 27 28 and 28 and opening valves 29 and 30, thehygroscopic drums 4 and 8 are cut out of the circult.

Recurring to Fig. 1, at 31 I show a highpressure air compressor, arranged by stages to compress air from atmosphere to about 50 atmospheres (or about 720 lbs. gage), and remove the heat of compression by the cooler I 32; then by opening valve 33 this highlycompressed'air is passed through pipe 34 into and through the calcium chlorid drum 4 and then through pipe 7 into and through the caustic potash drum 8-the calcium chlorid absorbing moisture and the caustic pothsh absorbing more moisture and the carbonic acid gas from the air. Then by opening valve'35 (valve 36 being closed) the air is conducted through pipe 37 into the CO freezing drum 38. This freezing drum (38) is. a part of a system of mechanical refrigeration, for freezing out the remaining traces of moisture left in the air, and serves also as an auxiliary cooler to bring the high-pressure air to be liquefied down to a low initial tem- 125 perature, so as to lessen the refrigerative work required of the returnflow air in the The system consists of the compressor 39, the 130 condenser 40 its lower end being connected through the pipe 41 with the liquid-gas pressure-releasing valve 42, and the descending evaporating pipe 43 and ascending vaporizing triple coils 44. Carbonic acid gas is preferably used in the system, and this gas,

evaporated from the liquid ()0 in the pipe 43 terchanger (51) at'this low temperature,

practically entirely free of moisture. The duplicate descending high-pressure helical coils 49 pass down around the core center 50 (in the expanded air passage 25 in the interchanger drum), and by the connecting pipe 52 deliver to the ascending triple helical coils 23, which connects with the descending triple helical coils 53 through pipe 23. These coils connect by pipe 54 with the submerged air-liquefying condenser 55; this condenser consisting of the closed drum 55 and coil 56 connecting with same at top and bottom. This condenser is located within the low-pressure evaporating vessel 57 which is inclosed by the vacuum insulation 58 Within the barrel 59-the vacuum being held by the air-tight sheet metal inclosure 60, from which the vessel 57 is formed. The condenser 55 has a liquid-air discharging valve 61, the inlet to which is the siphon tube 62, arranged so that only air after it is liquefied can be discharged from said condenser; said valve being operated by the outside hand wheel 63. At 64 I have an overflow outlet, controlled by the valve 65 and hand wheel 66.

The vacuum in the barrel 59 around the vessel 57, is produced preferably by filling the barrel 59 with CO gas, and then when the li uid air accumulates in the vessel 57,

this C 2 gas is quickly condensed to a liquid and collects in the annular catch 57 where it is prevented from reevaporating by the extreme cold. At 57 c I have a wire gage cup filled with charcoal to absorb any trace of air in the CO gascharcoal having great power ofabsorbing air when at extreme low temperature. In this Way almost a perfect vacuum insulation is-provided for the liquid air in vessel .57.

The cold expanded exhaust air from the expansion engine delivered from the conduit 21 is passed up, around and over the hi hly compressed air in the triple liquefying he ical coils 53, in a counter-current to the flow of highly compressed air in said coils; and as the air therein, compressed to or above its critical pressure, liquefies, it falls by gravity into the condenser when this condenser is filled, it is released from pressure and discharged into the evaporating vessel 57, thus submerging said condenser in the liquid air at substantially atmospheric pressure in said vessel. This evaporating liquid falls to a temperature of 3] 2.6 F., and quickly liquelies the cooled compressed air which has taken its place in the condenser; for such air being maintained at a tension at or above its critical pressure, it changes to a liquid at or below 220 without change of volume or the evolution of any heat. The vessel 57 being thoroughly insulated from outside heat by the vacuum 58, all heat for evaporating the liquid air therein must be drawn from the highly-eonipressed air in the submerged condenser 55 and liquel'ying coil 56. In the evaporating vessel 57 a surplus soon accumulates, which may be withdrawn from the system through the overflow tube 64. Once filled this low-pressure liquid air evaporating vessel (57) cannot be emptiedit can only -air from the system through the outlet 64;

and being constantly filled, the submerged high- )ressuro condenser (55 and 56) is constantly submerged in the evaporating liquid air therein.

It will be seen that the highly-com ressed air in the coils 53 and 23, which supp ice the submer ed condenser, is first subjected to the cooling action of both the vapor evapo rated from the low-pressure liquid air in yessel 57 and of the cold expanded air from conduit 21 exhausted from the engine; and then the compressed air of less tension being sup+ plied to said engine for expansion therein (in' coils 18) is also cooled by said outflowing cold exhaust therefrom and by the vapor or expanding air evaporated from the lowpressure liquidin said vessel (57). The last cooling effect of this expanded exhaust air and these cold distilled gases, is utilized in the pro-cooling drum 1.2 (see Fig. 1), in the helical passage 17, to cool the compressed air used in the engine closed circuit as it is received from the water cooler 2 and passes down through the triple coils 13. The surplus expanded air, over and above what the engine requires, is allowed to escape through the check-valve 67; and the eflicicncy of the process in operation is so high that the air thus escaping is rarely of lower temperature than the compressed air entering the precooler drum from pipe 11. At intervals of a few days any moisture in form of frost on the outside of the CO coils 44 and pipe 43, may be melted by hot air from the compressor 31 the water in cooler 32 being shut oil, valves 33, 35 and 68 being closco and valve 36 and cook 69 being opened. So also any frost in triple coil 13 in the pro-cooler (12) m be shutting off the Water from cooler 2, ant

. drawn from outlet 64.

melted by hot air from the compressor 1, by 1 closing valves 27, 28, and and opening valves 29 and 28 and drip cock 71. Drip cocks 72 and 73 are provided for draining the hygroscopic drums, 4 and 8. Power from an outside source may be supplied to the compressor fly-wheels 74, 75 and 7 6; and the power of the air-expanding engine A (Fig. 2)

.. may be utilized in helping to drive these com- 4 1 than the air to be liquefied, removing the heat pressors. The com ressor 31 takes in air through the check va ve 77; and the low- )ressure compressor takes air in through check valve 78. and valve 28 in starting up, or untilthe circuit is filled. The CO freezing drum (38) and the pre-cooler (12) and thermal interchanger low-pressure conduits 51, 79 and 80 with their connecting pipes, are all insulated against circumarnbient heat.

By my process I not only liquefy air, but partially separate the same into its constituent gases, oxygen and nitrogen, by fractional distillation in evaporating principally the nitrogen of the liquid air in the vessel 57, so

7 that the surplus liquid drawn from the tube 64 will be very rich in .oxygen, and the surplus gas escaping from check valve 67 will e correspondingly rich in nitrogen. The proportion of the two gases in the liquid drawn from the systemhowever, may be maintained practically the same as in the atmosphere, 21% oxygen and 7 9% nitrogen by closing valve 67 and opening valve 82 (see Fig. 1), when the surplus expanded gas in the return-flow pipe 26' will then be passed through pipe 81" and be re-compressed in the hIgh-PIGSSUIG com ressor 31, and only air enough will then e drawn in through the check valve 77 to make up for the liquid (See Fig. 2).

9- Having thus describedmy inventionwhat I claim as new and original and desire to secureby Letters Patent, is

1. The art or process of liquefying air consisting of or including, the compressing of the air to be liquefied to substantially its critical pressure, and the air to be used to cool and liquefy the same to a less pressure; the expansion of the last named air or that of relatively loW compression, against external resistance in a closed circuit; and then subjecting-the air to be liquefied or that of relatively high compression ,to the cooling action of said air of relatively-low compression after expansion of the same in said closed circuit. 2. The art or process of hquefylng air, consisting of or including the compressing of the airto be liquefied, tosubstantially its critical-- pressure, and removing the heat of compression therefrom; then compressing other and successive charges of air to less pressure than the air to be liquefied removing the heat of compression therefrom, and expand ing the same against external resistance and 65 then utilizing the said cold QXPQIldGClflll to cool, successively-first, the said cooled compressed air to be liquefied; and second, the said cooled air of less compression to be expanded.

3. The art or process of liquefying air, consisting of or including the compressing of the air to be liquefied, to substantially its critical pressure, and removing the heat of compression therefrom; then compressing other and successive charges of air to less pressure of compression therefrom, and expanding the same against external res1stance; and then utilizing the said cold expanded air to cool,

successively1'irst, the said cooled compressed air to be liquefied, and second, the

gas released from pressure and evaporated; -then compresslng other and successive charges of air to less pressure than that of the air to be liquefied, removing the heat of compression therefrom, and expanding the same against external reslstance; and ut1lizing the said cold expanded air to cool suc- 1 cessively,i irst, the said highly-compressed 'air to be liquefied, and second, the said air of less compression to be expanded.

5. The art or process of liquefying air, consisting of or including the com ressing of the air to be liquefied substantial y to or above its critical pressure, removing the heat of compression therefrom, and subjecting the same to the refrigerative effect of a liquid-gas released from pressure and evaporated; then compressing other and successive charges of air to less pressure than that of the air to be liquefied, removing the heat of compression therefrom, and expanding the same against external resistance; and utilizing the said cold expanded air to cool successively,fi rst, the said highly-compressed air to be liquefied, and second, the said air of less compression to be expanded,the said air of less compression to be compressed, cooled, ex anded and utilized as aforesaid, consecutively over and over in a closed circuit.

6. The art or process of liquefyingatmospheric air, consisting of or including the method of compressing air to a relatively high tension, and then cooling and liquefying the same Without reduction of pressure by cold air of substantially atmospheric pressure, after its expansion against external resistance from a less compression than the air cooled and liquefied.

and expanded therefrom in said engine against external resistance.

8. The art or process of liquefying atmospheric air, consisting of or including the method of compressing air to a relatively high tension, and then cooling and liqucfying the same without reduction of pressure by cold air of substantially atmospheric pressure, after its expansion against external resistance from a less compression than the air cooled and liqueficd saidcooling action being re-inforccd or augmented, in refrigerw tive effect, by the vapor and cold expanding gases evaporated from low-pressure liquid air reviously liquefied at relatively high tension as aforesaid.

9. The art or process of liquefying atmospheric air, consisting of or including the method of com ressing air to a relatively high tension, an then cooling and liquefying the same without reduction of pressure by the low-pressure cold exhaust air from an air-expansion engine, previously compressed to a less tension than the air being liquefied, and expanded therefrom in said engine against external resistance-said cooling action of said expanded exhaust air being reinforced or augmented, in refrigerative effect, by' the vapor and cold expanding gases evaporated from lowressure li uid air previously liquefied'at re atively big 1 tension as aforesaid.

10. The art or process of liquefying atmospheric air, comprising the compressin of air substantially to or above its critical pres sure, and li uefying it at that tension by the cold expan ed air exhausted from an airexpansion engine, supplemented or augmented in refrigerative effect by the vapor and cold expanding gases evaporating from liquid air of substantially atmospheric pressure.

11. The art or process of liquefying atmospheric air, comprising the compressing of air substantially to or above its critical pressure, and liquefying it at that tension by the cold expanded air exhausted from an air-expansion engine, supplemented or augmented in refrigerative effect by the, vapor and cold expanding ases evaporating from liquid air of substantially atmospheric pressure; and then sub-cooling said newly liquefied air at said high pressure by subjecting the same to the refrigerative action direct of said evaporating low-pressure liquid air.

12. The art or process of liquefying atmospheric air, comprising the compressing of air to a relatively high pressure and liquefying it at said high tension by cold expanded air exhausted from an air-expansion engine, supplemented or augmented in refrigerative eil'eet by the vapor and expanding gases from liquid air of substantially atmospheric pressure, being evaporated by heat drawn from liquid air of said high tension previously lir ueficd as aforesaid.

13. The art or process of liquefying atmospheric air, comprising the compressing of air, and removing the heat of compression and moisture therefrom, then cooling the same by a eounter-current of cold expanded air exhausted from an air-expansion engine, re-inforeed or augmented in refrigerativc cii'ect by the vapor and cold expanding gases era orated from :1 charge of liquid air of su stantially atmospheric pressure; and then subjecting said cooled compressed air, without reduction of pressure, to the cooling action direct of said low-pressure evaporating liquid air charge.

14. The art or process of liquefying atmospheric air or other gases, which comprises compressing portions of gas to substantially at or above its critical pressure and liquefying it while at such high pressure byother portions of gas which has been regeneratively cooled by compression to a lower pressure and subsequent expansion.

15. The art or process of liquefying atmospheric air or other gases, which comprises compressing portions of gas to a relatively high tension and liqucfying it while at such high tension by other portions of gas which has been regeneratively cooled by compression to a relatively low tension andsubsequent expanslon against external resistance.

16. The art or process of liquefying atmospheric air or other gases, which comprises utilizing gas which has been regeneratively cooled by compressing it to a relatively low tension and then expanding it in an engine to liquefy other portions of gas which has been compressed to and while maintained at a relatively high tension.

17. The art or process of liquefying air or other gases, which comprises compressing gas to a relatively high tension and while at such high tension li u'efying it by other gas which is regenerative y cooled byalternately compressing it to a relatively low tension and then expanding it in a closed cycle.

18. The art or process of liquefying air or other gases, which comprises compressing the gas to a relatively high pressure and while at'such high pressure liquefying it by the refiigerative effect of gas regeneratively cooled in a closed cycle by first compressing it to a relatively low pressure, expanding it in an engine and then conducting it back in counter-current to the compressed gas supplied to the engine to be re-compressed.

19. The art or process of liquefying air or other gases, which comprises com ressing the gas to be 1i ucfied to substantia at or above its critica pressure and removing the heat of compression therefrom, compressing other portions of gas to a lower pressure and removing the heat of compression therefrom andthen expanding the same against external resistance, and utilizing the cold expanded gas thus obtained to successively cool the said compressed gas'of high pressure and the said gas of lower pressure.

20. The art or process of liquefying air, which comprises compressing the air to a relatively high tension and removingthe heat of compression therefrom, and compressing other portions of air to a lower tension and removing the heatof compression therefrom and then expanding the same in an engine and utilizing the cold expanded air from the engine to cool first the said air of high tension and then the said air of lower tension supplied to the engine.

21. The art or process of liquefying air,

' which-comprises compressing the air to a relatively high tension and removing the heat of compression therefrom, and repeatedly compressing other air to a lower tension, removing the heat of compression therefrom, expanding the same in an engine and conducting it back to be again re-compressed, utilizing the return of the cold expanded air in counter-current thereto to cool first the said air of relatively high tension and then the said air of lower tension.

22. The art or process of liquefying atmospheric air or other gases, -which comprises compressing such air or other gas substantially to or above its critical pressure and while at such high pressure liquefying it by the refrigerative effect of as regeneratively cooled by compression su ostantially below its critical pressure and expansion in an engine, supplemented or augmented by the vapor from previously liquefied gas at substantially atmospheric pressure.

23. The art or process of liquefying air or other ases, which comprises compressing the gas su stantially to or above its critical pressure and while at such high pressure liquefying it b the refrigerative effect of gas regenerative y cooled by compression to a pressure below its'critical pressure and expansion in an engine, then withdrawing successive portions of the gas thus liquefied, reducing its 7 pressure to substantially atmos heric pres sure, and utilizing the vapor t erefrom' to supplement or augment the refrigerative effect of the said cold expanded gas from theengine to liquefy succeeding portions of gas of high pressure su plied to replace the liquefied gas thus Withdrawn.

24. The art or process of liquefy'ing air or other gases, which comprises compressing the gas substantially to or above its critical pressure and while at such pressure liquefying it by the combined refrigerative effect of cold expanded gas exhausted from an engine and previously liquefied gas evaporating at substantially atmospherlc pressure.

25. The art or process of liquefying air or other gases, which comprises compressing the gas substantially to or above its critical pressure and while at such pressure liqucfying it .gas to a relatively high pressure and while at such tension liquefying it by the combined refrigerative effect of gas which has been regeneratively cooled in a closed cycle by compressing it to a relatively low pressure expanding it in an engine andconducting it back to the compressor. in counter-current to the compressed gas Supt plied to the engine, and of previously lique ed gas evaporating at substantially atmospheric pressure.

27. The art or process of'liquefyingair or other gases, which comprises compressm Y the gas to a relatively high pressure and whi e at such tension liquefymg it by the combined refrigerative effect of gas which has been re generatively cooled in a closed cycle by compressing it to a relatively low pressure, expanding it in an engine, and conducting it ack to the compressor in counter-current t0 the compressed gas supplied to the engine,

and of previously lique ed gas evaporating at substantially atmospheric presssure; and maintaining the supply of the said liquefied gas at atmospheric pressure by the withdrawal of successive portions of the said gas liquefied at high pressure. I

28. The. art or process of liquefying air, which comprises compressing the air substantially to or above its critical pressure and liquefying it at that tension, and then withdrawing portions of the said liquefied air, reducing itspressure to substantially atmospheric pressure and utilizing 'thecold vapor therefrom'to liquefy and sub-cool the air at high pressure supplied to replace the liquefied air thus withdrawn.

29. The art or process of'li uefyrng air, which comprises compressing t e an to a relatively high tension and while at such tension liquefying it b effect of air which has een regeneratlvely cooled by'compression to a lower tension and ex ansion m an engine, and then successive y withdrawing portions of the air thus liquefied, reducing the pressure thereof to substantiall atmospheric pressure, and utilizingthe 00 d vapor therefrom to liquefy and sub-cool succeeding portions of air of 'high tension supplied to replace the liquefied air thus withdrawn.

30. The art or process of liquefying air, which comprises compressing the air to a tension substantially at or above its critical pressure and while at such tension liquefying 1t, then successively withdrawing portions of the liquefied air, reducing the pressure thereof to substantially atmospheric ressure and utilizing the cold vapor there rom, supplemented by the refrigerative effect of air which has been regeneratively cooled by compression to a pressure below its critical pressure and then ex anded, to liquefy succeeding portions of a1r at high tension supplied to replace the liquefied air thus wit drawn.

31., The art or process of liquefying air or other gas, which comprises compressing the gas substantially to or above its critical ressure and w ile at such high pressure iquefying it by the refrigerative efl ect of gas regenerativel cooled in a closed cycle by compressing 1t to a pressure below its critical pressure, expanding it in an engine, and conducting it back to be re-compressed in countor-current t0 the supply of compressed gas to the engine; and then successively withdrawing portions of the gas liquefied at high pressure, reducing the pressure thereof to I substantially atmospheric pressure, and utilizing the vapor therefrom to supplement and 1 augment the refrigerative effect of the gas exhausted from the engine.

32. The art or process of liquefying air or other gas, which comprises compressing the lgas substantially to or above its critical" 1 pressure, removing the heat of compression and moisture therefrom, and while at such high pressure liquefying it by the refrigerative effect of gas regeneratively cooled by compression to a pressure below its critical pressure and expansion in an engine, and successively sub-cooling and withdrawing the gas thus liquefied at high pressure and reducing its tension to atmospheric pressure in such a way as to utilize its refrigerative eiiect after withdrawal to sub-cool the li uefied gas of high pressure supplied to rep ace the liquefied gas thus removed.

Signed at New York city in the county of New York and State of New York this first day of November A. D. 1907.

JAMES F. PLACE.

Witnesses:

JOHN H. AoKRoYD, J. G. GADSDEN. 

